1. Field of the Invention
The present invention relates to a solid oxide electrolyte material and a method of producing a solid oxide electrolyte.
2. Description of the Related Art
Conventionally, a solid oxide fuel cell using an electrolyte material with oxygen ion as carriers comprises an electrolyte consisting of an ion conductor, and a fuel electrode and an oxidizer electrode disposed on both sides thereof by baking, or further comprises a metallic or ceramic porous support base disposed on one side of the fuel electrode and/or the oxidizer electrode.
It is general to use a zirconia (ZrO2) stabilized with yttria (Y2O3) (hereinafter often referred to as YSZ) as the electrolyte material, a nickel (Ni)-YSZ cermet produced by sintering NiO powder and the yttria-stabilized zirconia (YSZ) powder at a high temperature as the fuel electrode material, and a lanthanum-based perovskite composite oxide (LSM) as the oxidizer electrode material.
However, the high sintering temperature of the above-mentioned electrolyte material of about 1400° C. caused problems such as narrowing of the range of choices for components of the solid oxide fuel cell, reactions between other components, and an increase in cost due to limitation of an electric furnace or the like usable to the high-temperature process.
Conventionally, the following related arts are disclosed: A stabilized zirconia-alumina powder for solid oxide fuel cell including 5 wt % or less of high purity alumina dispersed to YSZ with a YSZ grain size/alumina grain size of 0.63 or more, a grain size of YSZ of 0.3 μm or less, and a grain size of alumina of 0.7 μm or less, which can be made to a solid electrolyte by sintering at about 1400° C. (refer to Japanese Patent Application Laid-Open No. 5-170444); a solid oxide fuel cell comprising a solid electrolyte consisting of a dense sintered body, comprising 1-15 atm % of at least one metal selected from manganese, iron, cobalt, nickel, copper, and zinc included in a solid electrolyte (YSZ) as an ion conductor (refer to Japanese Patent Application Laid-Open No. 6-103988); a ScSZ having a cubic phase as the dominant phase, which is obtained by adding 0.3-0.5 wt % of Al2O3 as a stabilizer to 8 mol % or more of ScSZ (refer to Japanese Patent Application Laid-Open No. 7-6622); a zirconia electrolyte powder capable of accelerating a solid phase reaction, which comprises 5 wt % or less of high-purity alumina powder added to a zirconia electrolytic powder including a dopant and having a sodium or sodium-based compound content of 2 wt % or less (refer to Japanese Patent Application Laid-Open No. 7-149522); a starting material for sintering consisting of a powder obtained by mixing a low-melting point material with a high-melting point material hardly forming a compound followed by fusing, solidifying and pulverizing (refer to Japanese Patent Application Laid-Open No. 8-73275); a cell for a solid oxide fuel cell having a solid electrolyte containing an oxidizer consisting of at least either one of Al2O3 and Bi2O3 (refer to Japanese Patent Application Laid-Open No. 11-86885); a magnetic composition including a ferrite and a sintering additive free from boron such as silicate glass, which can be sintered at a low temperature (refer to Japanese Patent Application Laid-Open No. 2000-164417); and a ScSZ including Bi2O3 added as sintering additive (a solid electrolyte material with low-temperature sintering property) (Japanese Patent Application Laid-Open No. 2003-51321).